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From "Michael Han (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (ZOOKEEPER-2389) read-only observer doesn't load transaction log when transitioning to read-only
Date Mon, 13 Mar 2017 16:22:13 GMT

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-2389?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Michael Han updated ZOOKEEPER-2389:
    Fix Version/s:     (was: 3.4.11)
                       (was: 3.5.3)

> read-only observer doesn't load transaction log when transitioning to read-only
> -------------------------------------------------------------------------------
>                 Key: ZOOKEEPER-2389
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2389
>             Project: ZooKeeper
>          Issue Type: Bug
>    Affects Versions: 3.4.8
>            Reporter: Jason Rosenberg
>             Fix For: 3.5.4, 3.6.0
> I have rediscovered an issue, that was apparently posted a while back (link below). 
It seems that if I configure an Observer node to be enabled for read-only mode, with syncEnabled
= true, it properly syncs its transaction log with the quorum.  However, if I shut down the
quorum participants, and the Observer automatically transitions to read-only mode, it does
not load the saved transaction log, and thus rejects any client connection with a zxid >
0.  But If I restart the Observer node, it reloads it's persisted transaction log and serves
read-only requests at the latest zxid.  Is this the correct behavior? Things run fine if instead
of an observer, I do the same with a read-only participant.  In this case, it transitions
without issue to a read-only server, and serves the current transaction log.
> It seems to me this issue renders read-only observers completely useless.  What am I
missing here?
> I'm seeing this with 3.4.8
> It seems this was discovered and reported a long time ago here:
> http://grokbase.com/t/zookeeper/user/14c16b1d22/issue-with-zxid-during-observer-failover-to-read-only

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